1. Technical Field
The invention relates generally to use of branched chain amino acids and more particularly to the use of dipeptides including branched chain amino acids to reduce bitterness in orally-administrable nutritional products.
2. Background Art
Amino acids are the monomeric building blocks of proteins, which in turn comprise a wide range of biological compounds, including enzymes, antibodies, hormones, transport molecules for ions and small molecules, collagen, and muscle tissues. Amino acids are considered hydrophobic or hydrophilic, based upon their solubility in water, and, more particularly, on the polarities of their side chains. Amino acids having polar side chains are hydrophilic, while amino acids having nonpolar side chains are hydrophobic. The solubilities of amino acids, in part, determines the structures of proteins. Hydrophilic amino acids tend to make up the surfaces of proteins while hydrophobic amino acids tend to make up the water-insoluble interior portions of proteins.
Of the common 20 amino acids, nine are considered essential in humans, as the body caimot synthesize them. Rather, these nine amino acids must be obtained through an individual's diet. A deficiency of one or more amino acids can cause a negative nitrogen balance, wherein more nitrogen is excreted than is ingested as proteins are degraded faster than they are synthesized. Such a condition can lead to disruption of enzymatic activity and the loss of muscle mass.
A number of muscle-wasting conditions have been identified, for which treatment with amino acid supplements has proved beneficial. For example, cachexia is a severe body wasting condition characterized by marked weight loss, anorexia, asthenia, and anaemia. Cachexia is a common feature of a number of illnesses, such as cancer, sepsis, chronic heart failure, rheumatoid arthritis, and acquired immune deficiency syndrome (AIDS). In addition, it has been found that certain tumors may induce cachexia through the production of a 24 kDa glycoprotein called proteolysis-inducing factor (PIF). PIF decreases protein synthesis, activates protein degradation, and stimulates the ATP-proteasome-dependent pathway. It has been hypothesized that the decreased protein synthesis associated with PIF is the result of PIF's ability to block the translation process of protein synthesis. Another factor, Angiotensin II (Ang II) has shown similar effects and may be involved in the muscle wasting observed in some cases of cachexia. Other muscle wasting diseases and disorders are known, including, for example, sarcopenia, an age-related loss of muscle mass.
Treatment of conditions such as cachexia and sarcopenia often includes nutritional supplementation, and, in particular, amino acid supplementation, in an attempt to increase protein synthesis and/or counteract protein degradation. Branched chain amino acids (BCAAs), which include valine, leucine, and isoleucine, are especially useful in such cases, as they have been shown to function not only as protein building blocks, but also as inducers of signal transduction pathways that modulate translation initiation.
The wasting conditions above are just a few of the conditions, disorders, and diseases for which amino acid supplementation has proved beneficial. Amino acid supplementation has also been used to treat diabetes, hypertension, high levels of serum cholesterol and triglycerides, Parkinson's disease, insomnia, drug and alcohol addiction, pain, insomnia, and hypoglycemia. Supplementation with BCAAs, in particular, has been used to treat liver disorders, including compromised liver function, including cirrhosis, gall bladder disorders, chorea and dyskinesia, and kidney disorders, including uremia. BCAA supplementation has also proved successful in the treatment of patients undergoing hemodialysis, resulting in improvements in overall health and mood.
Unfortunately, BCAAs exhibit a strongly bitter taste. Some patients reject oral nutritional supplements containing BCAAs because of their objectionable taste, despite the physiological benefits such supplements offer. Attempts to overcome such rejection have included the addition of masking agents to the supplement, which attempt to block the perception of bitterness, and the addition of other strong flavors, such as chocolate mint. Neither of these attempts has proved satisfactory. Masking agents generally do not completely block a patient's perception of bitterness and the addition of other strong flavors, while not bitter, are often equally objectionable to patients with limited appetites and/or nausea.
Accordingly, there is a need in the art for an orally-administrable nutritional product and method for its administration that do not suffer from the deficiencies above.